Thermal-controlled circuit-control mechanism



March 17, 1931. H. BRADLEY ET AL 1,797,126

THERMAL CONTROLLED CIRCUIT CONTROL MECHANISM Filed Aug. 30 1926 TTORNEY Patented Mar. 17,1931

UNITED STATES PATENT OFF-ICE HARRY BRADLEY AND GUSTAV 0. WILLIS, OF MILWAUKEE, -WISCONSIN; SAID WILMS ASSIGNOR TO LYNDE BRADLEY, OF MILWAUKEE, WISCONSIN THERMAL-CONTROLLED CIRCUIT-CONTROL MECHANISM Application filed August 30, 1926. Serial No. 132,522.

The invention relates -to thermal-controlled. circuit control mechanism.

The usual' method of eifect-ing the control of thermal-controlled circuit control mechanism is to supply heat to the heat-responsive element by means of a hot wire or resistance element associated with the circuit to be controlled. Such a method of heatcontrol has been found to have decided disadvantages from amanufacturing standpoint in devices of this kind because separate heating elements have to be used for different circuits having difi'erent current values, with .the result that a great variety of these elements have to be kept in stock to meet the demands of the trade, and with the further result that if the circuit is changed after its installation to increase or decrease its carrying capacity the user must get new heating elements to take .care of this change, unless it be a comparatively minor one. Furthermore, such heating elements not infrequently burn out and have to be replaced. The main ob ject of the present invention is to provide a novel method of supplying heat to the thermal-responsive element by a secondary curp rent induced by magnetic lines of force which are produced by the circuit to be controlled, with provision for varying the heating effect to accommodate different load conditions by varying the intensity of the magnetic field.

The invention further consists in an improved form of thermal circuit control mechanism associated with the heating means, and also in other features hereinafter more particularly described and claimed.

In the drawings Fig. 1 is a plan view of a device embodying the invention, with the upper cover plate for the switch mechanism removed; 1 1

Fig. 2 is a sectional view taken on the line 22 of Fig. 1;

Fig. 3 is a detail sectional view taken on the line 33 of Fig. 2;

Fig. 4 is a detail enlarged sectional view taken on the line 4-4 of Fig. 2;

Fig. 5 is a detail sectional view taken on the line 55 of Fig. 2;

Fig. 6 is a plan view showing a modification of the cut-out switch;

Fig. 7 is a similar View showing another modification of the cut-out structure.

In the drawings the numeral 8 designates the heating element which is instanced here as a copper sleeve whose lower portion is associated with the field of a magnetic circuit. The sleeve 8 is mounted in a: support 8 of insulating material havingspaced projections engaging the sleeve, as shown in Fig. 5. The magnetic flux is produced by energizin coils 9 and 10 suitably insulated from eac 1 other and mounted on a spool 11 of insulating material associated with amagnetic circuit which in this instance follows the path of the screw core 16 and the U-shaped bar 12 of magnetic material secured by screws 12 to a support S. -.The upper leg of this bar, to which the support- 8" -is' secured by screws 10, has an opening 13 through which the sleeve 8 projects into the hollow sleeve 11 and from which it is spaced, and the lower leg has a threaded bore 14 in which the threaded shank 15 of an adjustable core or ole 16 is mounted. The upper end of the adjustable core 16 is of a somewhat smaller diameter than the inner bore 17 of the sleeve 8 and is centered therein and spaced therefrom by a serrated disk 18 of insulating material secured to the top of said core and forms the other end of the iron path of the magnetic circuit in this instance. The coils 9 and 10 may be used singly or together, and when together being connected up in the circuit to be controlled either in series or in parallel so that four possible combinations with the circuit to be controlled are possible. to wit: first, a single coil. as the coil 9. associated with the circuit to be controlled; second, a single coil 10 associated with the circuit to be controlled, the disposition of these coils relative to the heat-contacting element 8 making a difference in magnetic intensity and thus adapting the devicefor circuits of different current value; third, a parallel arrangement between the coils 9 and 10 with the circuit to be controlled; and fourth, a series arrangement of these coils with the circuit to be controlled. Thus it is possible to provide certain quantitative energizing cur-' rent values for producing a magnetic flux by which induced currents are generated in the heating member 8, and for any one of these arrangements a final adjustment of the current'values is obtained by adjusting the position of the core 16 relative to the sleeve, this adjustment being facilitated by a scale 16 provided on the spaced legs 17 of a bracket 18 secured to the lower leg of the member 12 and the scale cooperating with the bottom or lower surface 19 of the knurled head of the core member.

To maintain the core member in adjusted position a series of longitudinally-extending grooves 20 are provided in said core member and a spring pawl 21 is adapted to engage in any one of the grooves brought into register therewith.

lVith this construction it will be noted that when current is flowing in the circuit to be controlled, thereby energizingone or both v,ot' the coils 9 and 10, a magnetic field is set up and the lower portion of the heating member 8 being located in this field currents are generated in this member and these currents provide a source of heat for heating said member whichupon being heated eiiects or causes the operation of the circuit control mechanism. Thus the energizing coil linked with the mem her 8 by the associated magnetic field will act as a transformer to induce current in member 8.

This mechanism may be of various kinds. In Figs. 1 and 2 we have shown a circuit control mechanism of the type shown in United States Patent No. 997,838, to E. W. Leeper,

granted July 11, 1911, wherein a ratchet Wheel 22 is secured to a spindle portion 23 formedon the heating member 8 by means of solder or suitable fuslble metal 24. Normally the ratchet wheel 22 and the heating member 8 are joined together by a solder joint but when the current in the circuit to be controlled becomes excessive enough heat will be furnished to the member 8, in the manner previously described, so as to cause heating of the solder to a suitably plastic condition to'enable theratchet wheel to turn relative to the heating member Normally, due to the fixing of the ratchet wheel against rotation, a pawl 25, of insulating material and pivotally mounted by a pin 26 on a lever 27 pi 'oted on a pin 27 on the support 8, is held against movement and in turn has a part which presses against a spring contact arm 28 having a contact 29 associated with afixed contact 30 so as to hold said spring contact against the fixed contact, due to the pawl then having locked engagement with the ratchet wheel and held thereagainst by the tension of the spring 28. The pawl 25 has a part 25 working over the top of the ratchet wheel to prevent said wheel from working upwardly from its true position when it is loose from the heating member. The arm 28 and contacts 29 and 30 are part of a control circuit including conductors 31 and 32, and usually such a circuit is a pilot circuit for furnishing current to a magnetically-operated cut-out switch for the circuit to be controlled. So long as the solder joint between the ratchet wheel 22 and the heating element 8 remains rigid the contacts 29 and 30 are engaged, but as soon as the solder 24 is heated by an overload in the circuit to .be controlled, the ratchet wheel 22 is free to turn, with the result that the spring 28 forces it to turn with the pawl. This breaks the circuit between the contacts 30 and 29 which thereby effects an opening of the circuit to be controlled.

Instead of a solder joint we show in Fig. 6 a switch arm 28 in the form of a bimetallic element having a part 33 associated with the upper portion of the heating element 8, and under conditions of excessive current it is so heated as to cause the contact point 29 on said element to move away from the fixed contact 30 and thus break the control circuit, as shown in saidfigure.

A further modification wherein a bimetallic element is used is shown in Fig. 7 wherein the numeral 34 designates the bimetallic element anchored at one end to a casing 35 and hearing at its other end against a projection 36 of a pivoted lever 36 which has a spring 37 associated therewith and a projection 38 of insulating material engageable with a spring switch arm 39 having a contact 40 engageable with a fixed contact 41 in a cutout pilot circuit including conductors 42 and 43. The bimetallic element 34 has a portion 44 thereof closely associated with the upper end 23 of the heating n 1en1ber so that under excessive current conditions the heat from the member 23 is conducted to the bimetallic element 44, causing it to elongate or unwind in a clockwise direction and thus free itself from projection 36" on the lever 36 so that the spring 37 moves said lever and projection 38 downwardly with reference to Figure 7 and away from the spring contact arm 39 to permit said spring arm to open the circuit between contacts 40 and 41.

In any of the above constructions the breaking of the circuit through cut-out switch mechanism effects the opening of the circuit to be controlled and this in turn cuts off the supply of current to the coil or coils producing the magnetic flux and thus the arm 28', to break the circuit between contacts g nular air gap, which airgap is continued" 29 and 30, as previously described, and the switch arm 39 tends to separate the contacts and 41 and the spring 37 tends to move the arm 36 so as to move the projection 38 away from the switch arm 39. Under normal circuit conditions the bi-metallic element 4% abutting against the projection 36' of the lever 36 overcomes the tensioning of said lever 36 and the opening pressure of the switch arm 39 so that the circuit is closed. As soon,

however, as an overload causes the sleeve 8 to heat the bi-metallic element 44 expands and this permits the spring 37 to move the lever 36 clockwise, with the result that switch arm 39 is free to move to a circuit-opening position. As soon as the element 44 cools it is in a position to snap against the projection 36 when the lever 36 is moved back toa posi tion in which the projection 38 acts on the member 39 to close the switch contacts 40 and 41.

We find that the best results are obtained by having the heating element thermally insulated from parts, particularly metallic parts, which would tend to convey the heat away by conduction. At the same time it is desirable to make provision for preventing cumulative heating of the heating element under normal operation, preferably by permitting small a1r convectlon currents to flow I around it and through it, and we have, therefore, shown the heating element 8 as separated from the tube 11 to provide a small anupwards through the upper portion of the upper leg of the bar 12, and through openings formed by the spaced projections holding the heating element 8 on the support 8, as shown more particularly in Fig. 5. lProvision is also made for convection currents flowing inside the heating element by having the insulating disk 18 provided with serrated edges, as shown in Fig. 4, thus providing air spaces 16. Furthermore, the grooves 20 permit air to flow upwardly between the pole 16 and its connections into the space between the poles. The air currents are thus permitted to flow up through the annular spaces, as aforesaid," and through the openings 46 and out through the opening 4:?

'in the top of the heating element-18. Thus while the heating efiect upon the heating member is localized to this member through its direct connection only 'with the support 8 so as to obtain efiicient heating on proper overload conditions, the small convection air currents circulating around through this member keep its temperature below operating temperature under normal operating conditions, as without some such provision for taking away the heat which is generated bythe induced currents in the heating element during the normal operation of the circuit being controlled, the heating element might in time become sufficiently hot to cause a shutting off of the current, because the accumulated heat might ultimately cause the operation of the heating element unless some means were provided for its dissipation. In order that these cooling convection currents may not be too large, it is desirable that the heating element be enclosed in a box formed by a recess in the support 8' and a pivoted cover 48. The device is not aflected by the inrush of starting currents nor by momentary overloads of fair size, nor by moderate overloads for reasonably continued periods, but operates rapidly upon a heavy overload where the motor winding would be injured. Furtherw more, our improved device can be setvery, accurately and is reliable in that it will repeat time and again very accurately and does not have to be set nor calibrated from time to time. It-retains its setting. It issimple and rugged in-construction and reliable in opera tion. The heat-control element permits momenta'ry overloads andnormal starting .currents oil-alternating current motors without functioning; at the same time it is readily responsive to abnormal overloads and when used with a three-phase motor will absolutely prevent the motor from burning out when running on single phase.

In order to prevent tampering with the adj ustment of the device, locking means may be provided to prevent substantial readjustment of the pole piece, and for this purpose we show a wire 48' looped through a hole 49 in the core member and one of a series of holes 50 in the bracket 17 and having its ends secured together by a lead seal 51.

While we have shown the heating element 8 as located in the gap between the poles, it will be understood that such heating element may be associated with the magnetic circuit netic field and having a fixed position relative thereto whereby heating currents are induced 'in said member of a value dependent upon the position of said core.

2. In a circuit control mechanism, the com bination of an electromagnet energized when the current in the circuit being controlled is flowing, an air gapinterposed in the magnetic path a the field of said magnet, a heating member positioned in said airgap, and a support for said member of heat-insulating material having spaced portions forming air channels associated with the air gap in the magnetic path of the magnetic field.

3. In a circuit control mechanism, the combination of an electromagnet energized when the current in the circuit being controlled is' flowing, a conducting path for the field of said magnet, an adjustable core for varying an airgap interposed in said path, a heating member linked with the electromagnetic field and heated independently of the coil of said electromagnet by current induced insaid member by said field, and an indicating scale associated with the adjustable core. 4. In a circuit control 'mechanism, the combination of a heat-conducting control member, an electromagnet having its field associated with the circuit to be controlled and inductively associated with said member to' impart heat thereto, a ratchet having a fusible joint connection with said heating member, a pivoted lever, a pawlfof insulating material carried by the lever and engageable with the ratchet, and a circuit-closing spring contact memberengaged by said pawl;

5. In a circuit control mechanism, the combination of" a heat-conducting control member, an electromagnet having a plurality of energizing coils adapted to be associatedwith the circuit to be controlled, either singly or in combination, and inductively associated with said heat-conducting control member, whereby the same device m'ay beused on circuits of widely varying loads.

6. In a heat-operated overload relay, the combination of a U-shaped frame of magnetic material, a plurality of solenoid coils mounted therein, a heat-operated switch mounted thereon including a tubular heating element, and an adjustable core of magnetic material mounted upon and adjustable with respect to said U-shaped frame and having a pole adapted to enter the heating element a predetermined amount at the will of the operator.

7. In circuitcontrol mechanism, the combination of a transformer having a variable ajr gap including a heating controlmember located within the air gap and forming the secondary of the transformer, and a primary associated with the circuit being controlled and having an adjustable core.

8. In a circuit control mechanism, the combination of an electromagnet energized when the current in the circuit being controlled is flowing and having an air gap in its magnetic field, a tubular heating member positioned in said air gap, means for supporting said member in spaced relation to the metal portions of said electromagnetto provide for cooling currents passing by the outside and within said tubular member.

9. In a circuit control mechanism, the combination of an iron-clad electromagnet energized when the current in the circuit being controlled is flowing and having an adjustable core member providing a variable air gap in its magnetic field, a tubular heating member positioned in said air gap With the outer end of said core. working therein but spaced therefrom. toallow cooling currents topass through its interior, andmeans for supporting said member in spaced relation to the iron-clading of said magnet to pro- .vide for cooling currents passing by the out- 11. In a circuit control. mechanism, the' combination with a winding associated with the circuit to be controlled and a core forming a magnetic field for the winding and having an air gap therein, switch mechanism interposed within the circuit to be controlled and including means operable upon heating thereof "beyond a predetermined degree, and a member disposed in the air gap of the magnetic field and thermally associated with said switch means whereby magnetic flux set up in the magnetic field upon energization of the winding thermally influences said member which in turn heats said switch means. j i

12. In a circuit control mechanism, the combination with a winding adapted tobe energized when the current in the circuit to be controlled is flowing, a magnetic field associated with the winding, an air gap interposed in the magnetic field of the winding, switch mechanism adapted to disrupt the circuit to be controlled upon being subjected to a heat exceeding a predetermined degree due to the occurrence of a predetermined overload in the circuit, a heat conducting member positioned in the air gap, and means associating the heat conducting member withthe switch mechanism wherebyupon the occurrence of an overload in the circuit to be controlled in excess of said predetermined degree-the heat conducting member raises the temperature of the switch mechanism beyond said predetermined degree to disrupt the circuit. 7 13. In a circuit control mechanism, the combination of a winding associated with the circuit being controlled, a magnetic field associated with the winding, a heat conducting member located within an air gap in the magnetic field whereby flux induced in the field by nergization of the winding heats said member, and circuit breaking mechanism incor-.

porated in the circuit to be controlled and operable upon the temperature of the heat conducting member exceeding a predetermined degree to disrupt the circuit.

14. In a circuit control mechanism, a winding associated with the circuit to be controlled, a core for the winding providing a magnetic field associated with the windm in, which flux is set up upon energization 0 the winding by current flowing in the circuit to be controlled, the magnetic reluctance of said magnetic field being constant, an air gap in the magnetic field, switch means for disrupting the circuit to be controlled-upon the occurrence of an overload therein in excess of a redetermined degree, a heat conducting mem r positioned in the air gap and adapted switch to control the openin thereof, a wind- 7 ing associated .with the circuit to be controlled and having a magnetic field provided with an air gap, said heat conducting element being positioned within the air gap whereby the I pulsating magnetic flux setup in the magnetic field by energization of the winding by the flow of current through the circuit raises the temperature thereof conditions in said circuit. In testimony whereof we afiix our signatures.

' HARRY L. BRADLEY. GUSTAV owners.

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